Preparation of compounds of fluorine



Patented Apr. 9, 1940 UNITED PATENTEIOFFFHCE I PREPARATION OF COMPOUNDS F FLUORINE Carl F. Swinehart, Gleveland Heigh'ts, Ohio, asn -signorto 'The-Harshaw Chemical Company, a Elyria, Ohio, a corporation of Ohio No Drawing. lApplication November 14,1938,

l 1 ,Serial No. 240,336

- '9 Claims. (01.23-88) Y This reaction is characterized by the requirement of a high temperature and the formation of a troublesome retort residue. Also a large proportion (68%) of the sulfuric acid functions for "m binding the large amount of by-product water.

This reaction, furthermore, does not go to completion but gives a yieldof only about 30% in practice. a

- I have now discovered a process of producing :3 BFs which can be carried out at relatively low temperature, forms no troublesome retort residues, forms a lesser amount of by-product water, and goes nearly to completion. My improved process consists in reacting together suitable ma- :m terials capable of forming a desirable ammonium boron trifiuoride complex, evaporating the reac-. tion mixture to a solid state and reacting on the said complex remaining with sulfuric acid (preferably fuming). 3.7 A typical reaction illustrating my novel process may be written'as follows:

It will be observed that the amount of by-product water produced in Equation 1 is eleven ni'ols as compared to 17 in the prior art reaction above 5 noted. While this reduction in water content is important, it is a feature of greater importance that the process lends itself to the removal of most of the by-product water, before the addition of the sulfuric acid, by simple evaporation or 0 equivalent manipulation. In Equation 2 it will be noted that only one mol of sulfuric acid is required to bind the by-product water for 4 mols of BFs as against 17 in the prior art process for, the same amount of BF3. Even this may be re- 55 duced by the use of fumingsulfuric acid. I may I have found it more, practical however, to prefor example substitute for libel-129.004 in Equation 2 fuming sulfuric acid up to about 20% S013 concentration (20% ol'eum)", thereby reducing the amount of by-productfluoxy-boric acid, a com mon impurity in BFs. 5 In'Equation 1, instead of NH4FI-IF, I may use, NH F and HF, NHa and HF, or NH4OH and HF, and, in place of I-I3BO3,.I'.may use other boric acids, e. g. HBOz'or B203, in all cases adjusting the proportions so that there] are 3 atoms, of l0 fluorine to one of boron. By the use of the term boric acid I intend to include B203, H302, and

HaBOs, and-the other boric acids.

It has been known for sometime (J J Berzelius, cited in Mellor 5, 125.);that when'8 mols of 15" ammonium fluorideare heated'vvith- 1 mol of boric oxide, 2 mols of ammonium fiuoborate are formed, with liberation of ammonia and water,

, according to the followingrea ctio n:

" I have found howeveryth at'if instead of such ratio designated by Berzelius', therebe. reacted 12 mols of ammonium fluoride with 2 mols of boric oxide, ammonia and water are evolved, and there is produced what appears to be the novel com pound (NH4)2O(BF3)4,1this reaction-being as pare the novel, compound by'reacting 6 mols of ammonium bifluoride'and' 4 mols of boric acid, because in such reaction much less ammonia is evolved, and wasted, the reaction being as given v in Equation 1. r

In carrying out the process of Equation 1, I' may drive off nearly all the NH3 and H20, in which case the product should analyze about 84% 13.1%. I find it more practical, however, to :drive 40 off less thanall the NH: and H20 indicated by the equation and-to make a product containing from 75% to 83% BF3. I consider it Within the scope of my invention to producea product which is evaporated just enough to form a solid material and up to 84% BFs. This would be, roughly, from about 70% to about 84% BF3. Just what the state of combination of the elements contained in this composition may be, I do not know with certainty, and I therefore consider myim vention to cover, in addition to the described process, the reaction product in the various; stages of dessication, particularly whendessicated sufficiently to form a solid material, that is, from I about 70% to 84% BFa. The word contain is specify any state of physical or chemical combination.

The following specific examples will serve to illustrate the principles of the invention:

Example I To 136 pounds of 99% NI-LlHFz was added 100 pounds of boric acid. The charge became liquid at room temperature. The resulting liquid was evaporated to a sufilcient state of dryness to permit screening, suflicient heat being applied to accomplish this result in about three hours. The yield was about 140 pounds of a product analyzing about BFs. The resulting product was treated with about three times its weight of 20% oleum, the BF; evolved being cooled to a dew point below 40 C. at atmospheric pressure and compressed into cylinders for shipment.

Example II To 141 pounds of NHd-lFz was added pounds of. boric acid. The charge became liquid at room temperature; The resulting liquid was evaporated to a sufficient state of dryness to permit screening, sufficient heat being applied to accomplish this result in about three hours. The yield was about 145 pounds of a product analyzing about 70% BFs. The resulting product was treated with about three times its weight of 20% oleum, the BFs evolved being cooled 'to a dew point of below +40 C. at atmospheric pressure and compressed into cylinders for shipment. 35

Example III Example I was varied by evaporating further until the product yielded about pounds of material showing on analysis about 75% BFa.

By repeated additions of water and evaporation, the BFE content may be raised to almost the theoretical value for the compound (NI-I4)2O(BF3)4.

The cooling of the BFs product prior to compression efiects removal of constituents which interfere with compression, particularly fluoxyboric acid. v

Having thus described my invention, what I claim is:

l. A new composition ofv matter containing the elements NI-h. H20 and BFs, in the probable form of a mixture of (NI-IQzOiBFaM, NHs and H20, the same being a solid material at room temperature and containing boron and fluorine in amount and proportion approximately corresponding to 70% to 84% BF3.

- 2. Process comprising reacting ammonium bifluoride with boric acid, the proportions being such as toprovide approximately one atom of boron for each three atoms of fluorine.

3. Process comprising reacting ammonium bifluoride with boric acid, the proportions being.

such as to provide approximately one atom of boron for each three atoms of fluorine and evaporating the reaction mixture to a solid state.

4. Process comprising reacting ammonium bifluoride with boric acid, the proportions being such as to provide approximately one atom of boron for each three atoms of. fluorine and evaporating the reaction mixture to a BFs content of from 70% to 84% by weight. w

5. A new composition of matter comprising (NI-I4) 20(BFs)'4.

6. A new composition of matter, being a reaction product of an ammonium fluorine material and a boric acid material, being solid at room temperature and yielding on analysis boron and fluorine corresponding to a BFa content or" from 70% to 84% and capable of yielding BFs upon treatment with sulfuric acid.

7. In the preparation of compounds of. fluorine, reacting slightly more than 4 mols of boric acid with 6 mols of ammonium bifluoride, heating to evolve water and ammonia from the reaction product, then reacting upon the product with sulphuric acid, cooling the boron fluoride resultant, and compressing.

8. In the preparation of compounds of fluorine, reacting slightly more than four mols of boric acid with six mols of ammonium bifluoride, heating to evolve water and ammonia from the reaction product, then reacting the product with sulphuric acid, coolingthe boron fluoride resultant to a temperature below minus 40 C. to reduce the moisture content to the saturation value for water vapor at that temperature at one atmosphere pressure and compressing into a suitable container.

9. A new composition of matter, being a reaction product of an ammonium fluorine material and a boric acid material, containing boron and fluorine in approximately the ratio BFs but containing'at least as much boron as represented by that ratio, the said reaction product being solid at room temperature and yielding on analysis boron and fluorine in quantity corresponding to a BF: content of approximately 75% and capable of yielding BFa upon treatment with sulfuric acid.

CARL F. SWINEHART. 

